A fluid flow guided through a flow channel is deflected by a lateral pressure gradient in parallel to the end walls. Since the flow layers adjacent to the wall are deflected due to their lower speed to a greater extent than the flow layers at a distance from the wall, a secondary flow is formed which is superimposed on a main flow, thus resulting in pressure losses, among other things. Secondary flows of this type regularly occur in blade cascades of turbomachines, such as gas and steam turbines. The blade cascades include a plurality of blades or vanes which are situated next to one another in the circumferential direction and which are situated in a rotary-symmetric flow channel, and between which a blade channel is provided in which the secondary flows form when the fluid flows through. In the radial direction, the blade channels are each delimited by a radially outer housing-side end wall (outer boundary wall) and by a radially inner hub-side end wall (inner boundary wall). The boundary walls are formed by a stationary housing section, by a rotor section, by radially inner blade cover plates and/or by radially outer blade cover plates. In the circumferential direction, the blade channels are each delimited by a pressure side and a suction side blade wall. To reduce the secondary flows and channel eddies, contours in the form of elevations and/or recesses for influencing the flow are often introduced into the end walls.
A plurality of end wall contours is known from the related art. In WO 2010/068391 A2, EP 1 681 438 A2 and EP 1 712 737 A1, it is proposed, for example, to provide an elevation on the pressure side of the blade and a recess on the suction side of the blade. In contrast, in EP 1 955 410 A1 and EP 2 136 033 A1, it is proposed to situate an elevation on the pressure side as well as on the suction side. The end wall contour of EP 1 762 700 A2 provides that two pressure-side elevations and one recess extending between the elevations in the circumferential direction are provided. The end wall contour of WO 2009/112776 A2 provides that one recess and elevation each are provided on the suction and the pressure sides. These known end wall contours result in a reduction of the secondary flows, but there is a lot of room for improvement.